Vinyl silicone oil and methyl vinyl silicone rubber (green rubber) stored for a period of time is easy to yellow, this is because the vinyl in the air at high temperature oxidation results, in addition to the raw material D4 or DMC impure, impurities also cause yellowing, the following share some solutions to solve the solution of vinyl silicone oil and methyl vinyl silicone rubber yellowing.
1, The reaction temperature should not be too high, the general batch production should not exceed 160 ℃.
2, The vacuum tightness of the reactor must be good.
3, Vinyl capping agent or ring body quality should be good, Cl ion, impurity capping agent must be controlled below tens of ppm.
Moisture content is related to polymerization, but does not affect the yellowing, H2O is equivalent to the capping agent, the most products are mixed with room temperature vulcanized methyl silicone rubber. The lower the viscosity or the higher the vinyl content, the easier it is to yellowing, by doing the above three points, the general yellowing problem can be controlled, in addition, you can add antioxidants to increase the effect of yellowing resistance.